1. Field of the Invention
The present invention relates to a dipole antenna, and more particularly, to a dipole antenna formed on a substrate for transmitting a signal.
2. Description of the Prior Art
The usage of a general dipole antenna is determined by the effective bandwidth of the general dipole antenna. The broadest usage of the general dipole antenna is the integrated digital television broadband antenna applied on a general digital household appliance. As is well known in the art, digital household appliances typically require a bandwidth between 460 MHz and 860 MHz. However, the general dipole antenna barely achieves the required bandwidth of the general digital household appliance because of its structural limitations. The effective bandwidth of the general digital household appliance barely reaches roughly twenty percent of the required bandwidth. Additionally, this limitation results in significant limitations in the effective bandwidth of an integrated digital television broadband antenna and the usage of the general digital household appliance.
Please refer to FIG. 1, which is a diagram of a conventional dipole antenna 100. The dipole antenna 100 is formed on a substrate 102 for transmitting a first signal. As shown in FIG. 1, the dipole antenna 100 comprises a first radiator 104, a feeding line 106, a signal source 108, a ground line 110, and a second radiator 112. The feeding line 106 is connected to an end of the first radiator 104. The signal source 108 is connected to the feeding line 106 and utilized for providing the first signal. The ground line 110 is connected to the signal source 108. The second radiator 112 is connected to an end of the ground line 110. The dipole antenna 100 transmits and receives signals via the resonance between the first radiator 104 and the second radiator 112. In other words, the first radiator 104 and the second radiator 112 are a pair of resonant radiators. The lengths of the first radiator 104 and the second radiator 112 affect the bandwidths of transmitting and receiving signals. Therefore, the lengths of the first radiator 104 and the second radiator 112 are set to be a quarter of the wavelength of the first signal thereby providing efficient power consumption as the dipole antenna 100 transmits the first signal. The dipole antenna 100 thus transmits the first signal in a specific effective bandwidth. However, the specific effective bandwidth is only capable of reaching twenty percent of the required bandwidth as mentioned previously. Therefore, it is apparent that new and improved devices are needed for solving said problem.